<- Ancient GuitarfishVenospike Ray (Future Animal) -> Common Stingray - Amanda Chancellor
The Stingray (Dasyatidae) are not a species, they are a family, of 9 genera (6 sting rays, 3 river sting rays) and about 70 species. Stingrays are so named due to the barbed stinger on their tail. The stinger may reach up to 35cm long, some species have more than one stinger, and few species such as the Urogymnus Asperrimus do not have a stinger. The stingray I have chosen to research is the Common Stingray (Dasyatis pastinaca) In this report you will find information stating the adaptations that have been adopted by stingrays during their evolution from the ancient Guitarfish, to survive in the modern world, and also the Stingrays habitat, feeding and breeding patterns.
Image has been labelled by Amanda Chancellor, Original Image from - http://de.academic.ru/pictures/dewiki/68/Dasyatis_pastinaca01.jpg
Habitat
The Common Stingray is mostly found throughout the Black Sea and the Mediterranian, though it is also found throughout the North Eastern Atlantic, yet in significantly lower numbers, ranging from Norway and the Western Baltic Sea to Madeira and the Canary Islands.
File:Dasyatis pastinaca rangemap.png
They have also been seen in the Eastern Pacific along the coast of North America. They are seen all throughout these waters and are commonly seen near the shore, encountered by beachgoers and such.
The Common Stingray is usually encountered solitary, though sometimes in small 'social' groups. It is generally more active at night, tending to bury itself in mud or sand during the day. It is a bottom dwelling species which usually is found in shallow water at around 60m deep, yet their habitats can extend from the shore line, to up to 200m deep. They prefer to live in sandy or muddy bottoms in calm water, where they can be seen to have buried themselves under the sand to camoflauge. They mostly swim along the bottom of the sea, so as to camoflage themselves easily, and also so that they can bury themselves
Stingray buried in sand - http://www.cdislands.com/photos_turkscaicos/gtr1/xgt11025.jpg
The common Stingray is also encountered in waters of lower salinity, as unlike most fish, its body can tolerate this. It is often found near rocky reefs or in estuaries and is most abundant in summer and least abundant in winter. They are found among reefs and estuaries due to the levels of food, and also they sometimes hide under the rocks or reefs, in thin crevices.
The Habitat of the Common Stingray links it to its food sources. It prefers to feed on a variety of organisms also living on the bottom of the sea, such as Crustaceans, Cephalopods, bivalves, polychate worms and small bony fish. Their abundance in the summer months also links to its mating patterns, in which the female has been reported to generally give birth between the months of May and September, following a 4 month gestation period. They tend to approach shallow inshore waters to give birth to their offspring.
Structural Adaptation 1 - Flatter Body Shape
The Common Stingray has structurally adapted to its environment through the size and shape of its body. Overtime its body has become distinctly flatter, in comparison to its ancestor the guitarfish. The flatter bodies of the common stingray allows them to effectively conceal themselves in their environment. The flat shape is very easy to conceal in the sandy areas which the live, as they can bury under the sand and be very hard to spot. With a larger and more rotund body shape it would be hard for the stingray to hide itself easily and convincingly, and also it could not fit as easily into the thin crevices of reefs, which it often does. The Flatter body shape has also allowed stingrays to travel more easily along the ocean floor as it has become more streamline. It is also easier for it to catch its prey as it can hide itself for longer, and then when it desires food, can simply dart upwards to retrieve this, with a whirl of sand arising as it does this, which further hides it, and makes it harder for the food to escape.
In guitar fish the shape of the upper body was more similar to that of a shark than the stingray we know today, the area which would be known as a ribcage in humans was much more defined and round in shape, but over time it has gradually become flatter, due to environmental pressures as a gradual change of habitat, and also the predators which hunt them have changed over time. Types of rays have been around since the time of the dinosaurs, and since then their predators and prey have changed substantially, and therefore their methods of concealing themselves have needed to become more suited to the current threats on the species.
Structural Adaptation 2 - The Tail
The tails of stingrays have evolved greatly over time. During the time of the ancient guitar fish the tails were wide, with fins being displayed in the centre, very similar to the dorsal fin on a shark, but much smaller. Over time the stingrays tail has become thinner and thinner, eventually becoming the whiplike feature we see today. This modern tail aids the stingray in its directional travel, and also it is very easy for the stingray to hide when it buries itself in the sand. One of the most important features of the modern stingray tail is that it contains venom. This has become the stingrays most vital weapon, as if anything seeks to attack it from above, or stands on it, this barb like tail can stab into the danger, whatever it may be, and injected into it. The tail can also move in more directions than the tail of the Ancient Guitarfish , being able to which lies flat on the ocean floor. One of the most important features of the modern stingray tail is that it contains venom. The toxin in stingrays tails is a type of protein which is present under the thin skin of the stingrays tail. The thin skin breaks on penetration and the toxin is released.
A common misconception of a stingrays tail is the the spines are at the end, but this is not true, the spines are at the base of the tail, and stingrays can have up to 5 spines. If a stingray loses a spine by defending itself a new one will immediately grow back. This adaptation may have occurred due to environmental pressures such as the change of the types of predators in the ocean and also as their habitats gradually changed the tail could not stay as what it was in the time of the guitarfish, their methods of camouflage have changed and the tail adapted to this, by becoming much smaller, and versatile. Also the presence of toxins may have occurred due to the rising need to protect themselves from the modern predators of the ocean, as the sharp tail was not enough.
Behavioral Adaptations 1 - Breeding Patterns (Giving birth in Shallower waters in Warmer months)
During the summer months, from May to September is when Common Stingrays are most likely to give birth, after a four month gestation period. They move to shallower, warmer waters until the pup is born away from the male partner, and gradually move back to the original habitat. This helps the Stingray as during the summer months the animals in which the Stingray feeds upon are more common and easily found, and therefore gives the offspring more food, and a higher chance of survival. They also move into shallower waters as there are fewer predators there to pose as a threat to the pup. Also being away from the males until the warmer months end ensures that mating will not occur again until the next year when the female will be able to give birth in the warm months to again give the pup the highest chance of survival.
Environmental pressures which could have given rise to the breeding patterns of the Common Stingray are that during the period from May - September the animals which the stingray hunts are much more common and therefore the pup will have a higher chance of survival, and also the fact that if they mate so that they give birth in Winter the pup may not survive, due to lack of food which would mean that they would have to hunt in deeper areas where there are more predators which may pose a threat to the offspring.
Behavioral Adaptations 2 - More Active at night
The common stingray is more active at night due to the fact that the animals which they feed on are more abundant at night,and also hunting at night is an advantage to them as they do not rely on their eye sight for hunting, they use their smell and Electroreceptors, which are just as affective at night as they are during the day. Stingrays need to camouflage themselves is more important and necessary during the day, as the light makes them easier to spot, and if they move around a lot they could be at risk from attack from predators. Although most underwater animals can see at night, they cannot see as well as they can during the day and therefore stingrays can move around without being very susceptible to attack. During the day stingrays usually bury themselves in sand or mud during the day as it is harder to hunt at this time and also is the most dangerous, although they will move and become active if danger is present or there is the need to leave where they are.
Environmental pressures which may have led to this could be the fact that the common stingrays colour does not blend in with the white/yellow sand of the ocean floor and if they hunt during the day they would be highly visible. Also at night on the reefs and estuaries where the common stingray is found, the animals which they feed are more active and common at night, which would lead to stingrays having a better chance of feeding at night due to lower visibility (they can use their electroreceptors) and more prey.
Physiological Adaptations - Smell and Electroreceptor
Stingrays cannot see their prey when they hunt, or when they are eating. They use to very clever detectors which over time have developed into the advanced and efficient method used today. Stingrays have low frequency Electroreceptors and Smell Detectors, which allow them to hunt and eat without the use of their eyes. Electroreception is the biological ability to receive electrical impulses. This system consists of many tiny gel canals positioned on the head of the stingray. These senses can also be used for detecting their environment, and almost like a compass, as it is believed that the electroreceptors can sense the earths magnetic field. These are vital adaptations although the Ray has always had a sense of smell, over time it has developed and strengthened, and the electroreceptors have evolved to become a very effective hunting and feeding mechanism. Stingrays undertake passive electroreception, where they can sense the weak bioelectric fields which are created by other animals, as opposed to active electroreception, where the animals senses its surrounding environment by sending out weak electric fields, of no more than 1 volt. The common stingray relies on its electroreception the most in the final stages of its attack, as they are able to sense the movements and environments immediately prior to their attack, which is a vital advantage.
Environmental pressures which could have given rise to the presence of Smell and Electroreceptor Detectors may be the fact that as stingrays habitat has gradually moved to the sandy areas around the edges of reefs etc, and their prey has become small animals which also live on the bottom of the ocean such as crabs and small fish, their eye sight, and the position of their eyes is not beneficial for their hunting needs and habits a more effective method gradually developed.
Common Stingray - Amanda Chancellor
The Stingray (Dasyatidae) are not a species, they are a family, of 9 genera (6 sting rays, 3 river sting rays) and about 70 species. Stingrays are so named due to the barbed stinger on their tail. The stinger may reach up to 35cm long, some species have more than one stinger, and few species such as the Urogymnus Asperrimus do not have a stinger. The stingray I have chosen to research is the Common Stingray (Dasyatis pastinaca) In this report you will find information stating the adaptations that have been adopted by stingrays during their evolution from the ancient Guitarfish, to survive in the modern world, and also the Stingrays habitat, feeding and breeding patterns.
Common Stingray
Habitat
The Common Stingray is mostly found throughout the Black Sea and the Mediterranian, though it is also found throughout the North Eastern Atlantic, yet in significantly lower numbers, ranging from Norway and the Western Baltic Sea to Madeira and the Canary Islands.
The Common Stingray is usually encountered solitary, though sometimes in small 'social' groups. It is generally more active at night, tending to bury itself in mud or sand during the day. It is a bottom dwelling species which usually is found in shallow water at around 60m deep, yet their habitats can extend from the shore line, to up to 200m deep. They prefer to live in sandy or muddy bottoms in calm water, where they can be seen to have buried themselves under the sand to camoflauge. They mostly swim along the bottom of the sea, so as to camoflage themselves easily, and also so that they can bury themselves
The common Stingray is also encountered in waters of lower salinity, as unlike most fish, its body can tolerate this. It is often found near rocky reefs or in estuaries and is most abundant in summer and least abundant in winter. They are found among reefs and estuaries due to the levels of food, and also they sometimes hide under the rocks or reefs, in thin crevices.
The Habitat of the Common Stingray links it to its food sources. It prefers to feed on a variety of organisms also living on the bottom of the sea, such as Crustaceans, Cephalopods, bivalves, polychate worms and small bony fish. Their abundance in the summer months also links to its mating patterns, in which the female has been reported to generally give birth between the months of May and September, following a 4 month gestation period. They tend to approach shallow inshore waters to give birth to their offspring.
Structural Adaptation 1 - Flatter Body Shape
The Common Stingray has structurally adapted to its environment through the size and shape of its body. Overtime its body has become distinctly flatter, in comparison to its ancestor the guitarfish. The flatter bodies of the common stingray allows them to effectively conceal themselves in their environment. The flat shape is very easy to conceal in the sandy areas which the live, as they can bury under the sand and be very hard to spot. With a larger and more rotund body shape it would be hard for the stingray to hide itself easily and convincingly, and also it could not fit as easily into the thin crevices of reefs, which it often does. The Flatter body shape has also allowed stingrays to travel more easily along the ocean floor as it has become more streamline. It is also easier for it to catch its prey as it can hide itself for longer, and then when it desires food, can simply dart upwards to retrieve this, with a whirl of sand arising as it does this, which further hides it, and makes it harder for the food to escape.
In guitar fish the shape of the upper body was more similar to that of a shark than the stingray we know today, the area which would be known as a ribcage in humans was much more defined and round in shape, but over time it has gradually become flatter, due to environmental pressures as a gradual change of habitat, and also the predators which hunt them have changed over time. Types of rays have been around since the time of the dinosaurs, and since then their predators and prey have changed substantially, and therefore their methods of concealing themselves have needed to become more suited to the current threats on the species.
Structural Adaptation 2 - The Tail
The tails of stingrays have evolved greatly over time. During the time of the ancient guitar fish the tails were wide, with fins being displayed in the centre, very similar to the dorsal fin on a shark, but much smaller. Over time the stingrays tail has become thinner and thinner, eventually becoming the whiplike feature we see today. This modern tail aids the stingray in its directional travel, and also it is very easy for the stingray to hide when it buries itself in the sand. One of the most important features of the modern stingray tail is that it contains venom. This has become the stingrays most vital weapon, as if anything seeks to attack it from above, or stands on it, this barb like tail can stab into the danger, whatever it may be, and injected into it. The tail can also move in more directions than the tail of the Ancient Guitarfish , being able to which lies flat on the ocean floor. One of the most important features of the modern stingray tail is that it contains venom. The toxin in stingrays tails is a type of protein which is present under the thin skin of the stingrays tail. The thin skin breaks on penetration and the toxin is released.
A common misconception of a stingrays tail is the the spines are at the end, but this is not true, the spines are at the base of the tail, and stingrays can have up to 5 spines. If a stingray loses a spine by defending itself a new one will immediately grow back. This adaptation may have occurred due to environmental pressures such as the change of the types of predators in the ocean and also as their habitats gradually changed the tail could not stay as what it was in the time of the guitarfish, their methods of camouflage have changed and the tail adapted to this, by becoming much smaller, and versatile. Also the presence of toxins may have occurred due to the rising need to protect themselves from the modern predators of the ocean, as the sharp tail was not enough.
Behavioral Adaptations 1 - Breeding Patterns (Giving birth in Shallower waters in Warmer months)
During the summer months, from May to September is when Common Stingrays are most likely to give birth, after a four month gestation period. They move to shallower, warmer waters until the pup is born away from the male partner, and gradually move back to the original habitat. This helps the Stingray as during the summer months the animals in which the Stingray feeds upon are more common and easily found, and therefore gives the offspring more food, and a higher chance of survival. They also move into shallower waters as there are fewer predators there to pose as a threat to the pup. Also being away from the males until the warmer months end ensures that mating will not occur again until the next year when the female will be able to give birth in the warm months to again give the pup the highest chance of survival.
Environmental pressures which could have given rise to the breeding patterns of the Common Stingray are that during the period from May - September the animals which the stingray hunts are much more common and therefore the pup will have a higher chance of survival, and also the fact that if they mate so that they give birth in Winter the pup may not survive, due to lack of food which would mean that they would have to hunt in deeper areas where there are more predators which may pose a threat to the offspring.
Behavioral Adaptations 2 - More Active at night
The common stingray is more active at night due to the fact that the animals which they feed on are more abundant at night,and also hunting at night is an advantage to them as they do not rely on their eye sight for hunting, they use their smell and Electroreceptors, which are just as affective at night as they are during the day. Stingrays need to camouflage themselves is more important and necessary during the day, as the light makes them easier to spot, and if they move around a lot they could be at risk from attack from predators. Although most underwater animals can see at night, they cannot see as well as they can during the day and therefore stingrays can move around without being very susceptible to attack. During the day stingrays usually bury themselves in sand or mud during the day as it is harder to hunt at this time and also is the most dangerous, although they will move and become active if danger is present or there is the need to leave where they are.
Environmental pressures which may have led to this could be the fact that the common stingrays colour does not blend in with the white/yellow sand of the ocean floor and if they hunt during the day they would be highly visible. Also at night on the reefs and estuaries where the common stingray is found, the animals which they feed are more active and common at night, which would lead to stingrays having a better chance of feeding at night due to lower visibility (they can use their electroreceptors) and more prey.
Physiological Adaptations - Smell and Electroreceptor
Stingrays cannot see their prey when they hunt, or when they are eating. They use to very clever detectors which over time have developed into the advanced and efficient method used today. Stingrays have low frequency Electroreceptors and Smell Detectors, which allow them to hunt and eat without the use of their eyes. Electroreception is the biological ability to receive electrical impulses. This system consists of many tiny gel canals positioned on the head of the stingray. These senses can also be used for detecting their environment, and almost like a compass, as it is believed that the electroreceptors can sense the earths magnetic field. These are vital adaptations although the Ray has always had a sense of smell, over time it has developed and strengthened, and the electroreceptors have evolved to become a very effective hunting and feeding mechanism. Stingrays undertake passive electroreception, where they can sense the weak bioelectric fields which are created by other animals, as opposed to active electroreception, where the animals senses its surrounding environment by sending out weak electric fields, of no more than 1 volt. The common stingray relies on its electroreception the most in the final stages of its attack, as they are able to sense the movements and environments immediately prior to their attack, which is a vital advantage.
Environmental pressures which could have given rise to the presence of Smell and Electroreceptor Detectors may be the fact that as stingrays habitat has gradually moved to the sandy areas around the edges of reefs etc, and their prey has become small animals which also live on the bottom of the ocean such as crabs and small fish, their eye sight, and the position of their eyes is not beneficial for their hunting needs and habits a more effective method gradually developed.
http://www.biodiversityexplorer.org/chondrichthyes/glossary.htm - Glossary of terms on Sharks and Rays, retrieved on 17th July 2010http://www.elasmo-research.org/education/evolution/rise_modern.htm - Elasmodiver Rise of the Modern Sharks and Rays, Retrieved 20th June 2010
http://www.elasmodiver.com/CommonStingray.htm - Elasmodiver Common Stingray, Retrieved on 20th June 2010
http://www.elasmodiver.com/elasmobranch_evolution.htm - Elasmodiver Evolution of Sharks and Rays, retrieved on 29th June 2010
http://www.lifeunderthesea.co.uk/id59.htm - Life under the sea - Family, Retrieved on 18th June 2010
http://www.flmnh.ufl.edu/fish/education/adapt/adapt.htm - How fish use adaptations, Retrieved on 24th June 2010
http://en.wikipedia.org/wiki/Electroreception - Wikipedia Electroreception - Retrieved on 2nd July 2010
http://www.nova.edu/ocean/ghri/chapman03.pdf - Mating Behaviour of Common Stingrays, Retrieved on 1st July 2010
http://www.springerlink.com/content/g168t61t4hw00542 - Behaviour of Animals with low frequency Electrosensory Systems - Retrieved on 2nd July 2010